I'm trying to override one specific function in voip module. So far, I can see no error is being thrown in debug mode but my changes are not being shown either.

Here's my code (two options have been tested unsuccessfully):

odoo.define('MYMODULE.user_agent', function (require) {

    "use strict";

    var voip_user_agent = require('voip.user_agent');

    //OPTION 1

    //var UserAgent = voip_user_agent.UserAgent.extend({

    //OPTION 2

    var UserAgent = voip_user_agent.extend({    

        _sendNotification: function (title, content) {

            if (window.Notification && Notification.permission === "granted") {

                return new Notification(title,

                    {body: content, icon: "/MYMODULE/static/src/img/phone_ringing.gif", silent: true});

            }

        },

    });   

    //OPTION 1

    //voip_user_agent.UserAgent = voip_user_agent; 

    //OPTION 2

    voip_user_agent = voip_user_agent;

});

Can someone give me a hint on how to get this thing working?